Flowmeter



w. J. KINDERMAN 2,617,300

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4 ITCH SPIRAL'lucKNs-sa Patented Nov. 1l, 1952?l UNITED STATES PATENT OFFICEv FLONMETER Walter J. Kinderman, Philadelphia, Pa., assignor to Yarnall-Waring Company, Philadelphia, Pa., acci-poration of Pennsylvania 3 Claims.

My invention relates to means and methods for transmitting longitudinal motion within a Weir chamber or orifice subject to pressure into rotary movement outside the chamber through a pressure resistant wall.

A purpose is to operate an indicator or recorder from a weir or orice by a spiral magnetic armature through movement of a magnet alongV the length of the armature.

A further purpose is to provide spiral connection between a pressure-responsive element such as a diaphragm, bellows or float, responding to a characteristic such as liquid flow or level in a Weir or orifice, and an indicator through a magnet and magnetic armature, geared together magnetically to produce a result similar to worm and worm gear connection.

A further purpose is to use difference in pressure, such as characterizes difference in water levels in a weir` or the like or is present on opposite sides of an orifice in a fiow meter, for example, to shift the position of a magnet along the length of a rotary sp-iraled magnetic armature and to show angular movement of the armature upon an indicator.

A further purpose of the invention is to apply magnetic linkage between a magnet preferably of horse-shoe type movable, in response to a liquid characteristic in a weir or orifice, transversely to its flux and a rotatable spiral armature of magnetic material between the poles having its axis longitudinal to the direction of motion to secure rotary motion of the armature and connected parts. This is particularly useful because the magnet coupling is resilient and because it operates through pressure-resistant walls so that the magnet can be subject to pressure. and the armature free from pressure.

A further purpose is to provide effective and accurate connection between a pressure-sensitive element subject to differing pressures, one varying because of different water levels or both due to flow meter pressure drop, for example, and to indicate magnet movement through rotary armature actuation.

A further purpose is to provide effective and accurate connection between a pressure-sensitive element, subject to variable heads or to the two pressures on opposite sides of an orifice, and an indicator, while avoiding stufngfbox friction and other friction.

Further purposes will appear in the specification and in the claims.

I have preferred to illustrate my invention by a few forms only, selecting forms which are simple, practical, reliable, effective and inexpensive and which at the samey time well illustrate the principles involved.

The invention resides not only in the methods or processes which I apply, but in the mechanism by which the methods or processes may be carried out.

Figure 1 is a central vertical section of a preferred form of the indicating element of. my invention.

Figure 1a is a fragmentary section applying, to the structure of Figure 1, a modified form of pressure-responsive element.

Figure 1b is a reduced` scale fragmentary illustration of aformmodied as compared with Figure 1.

Figure 2 is a reduced scale section of Figure 1, taken on line 2-2 of Figure 1.

Figure 3 is a reduced scale perspective view of a portion of the structure of Figure 1, capable of use also with the structure of Figure la.

Figure 4 is a reduced scale central longitudinal section of a second form of indicator element of my invention, taken upon line 4 4 of Figure 5.

Figure 5 is a section` of Figure 4, taken upon line 5 5 of Figure 4.

Figure 6 isa diagrammatic elevation, partly in section showing the invention applied to flowmeter measurement of a liquid passing through an orice.

Figure 7 is a fragmentary elevation partly in section showing the invention applied to recording now through a weir notch.

Figure 8 is a fragmentary front elevation of a V-notch weir such as could be used in Figure '1.

Figure 9 is a side elevation or top plan view of one of many possible forms of follower or armature to correct in the armature where the variation in rate or quantity of flow or other liquid characteristic is not the same at all parts of the armature for equal movements of an operating magnet. This may be applied to any of the forms, particularly Figures 6 or 7.

Figure 10 is a front elevation of a pen recording device operating on a travelling sheet by which any of the ow indicating structures can be made recorders.

Figures 11, l'la; 12, 12a; 13,r 13a and 14, 14a are schematic figures arranged in pairs and illustrating conditions concerningthe poles and the spiral armatures as they apply to previously existing structures.

Figures 15, 15ad and 16, 16a are corresponding pairs of schematic views relating to the present invention.

Figures 17, 18, 19, are schematic views showing relations existing between the poles and the armature in the present invention.

The present application is a continuation in part of applicants previous application, Serial No. 388,134, led April l1, 1941, now abandoned, and a division of applicants previous application, Serial No. 517,242, filed January 6, 1944, for Differential Pressure Gauge, which matured into Patent Number 2,509,644 on May 30, 1950.

The pressure sensitive element in some of the forms uses a pressure area or surface which is exposed to fixed and variant opposed (hence differential) pressures from a Weir, orice or the like. It acts against a restraining force which increases uniformly with progressive displacement of the pressure area.

The preferred form among those shown in a diaphragm subject `to the opposing pressures, using a flat cantilever spring as the restraining force.

It is evident that various other forms will carry out my broad invention and I have illustrated several. Y

A metal bellows (Figure 1a) of spring material of proper proportions could be used instead of the diaphragm.

A magnet float within a mercury pool is cheap and effective, part of the pool being subject to one of the differential pressures and part exposed to the other pressure.

The operating mechanism for my preferred form of indicator, that of Figures 1, 2 and 3 is enclosed within a housing i5 and cover i6 united by bolts i? and sealed by annular packing i8, i9 lying on opposite sides of a diaphragm support E@ apertured at 2|.

rhe diaphragm support for convenience is recessed at 22 on the side toward the housing body 23 in order to permit a well, later described, to fit down into the recess.

Because the liquid whose flow or level is to be indicated does not enter the housing but produces its effect in alterationof effective pressure to be exerted upon the diaphragm through fluid piped to the housing from a distance, there is no requirement that the housing be placed in any particular position .with respect to the vertical or horizontal. It is therefore assumed to be mounted vertically from any suitable bracket by a bolt entering threaded opening 24. This corresponds with the showing in Figure 1. The indicator used may therefore be attached to the front face of the housing where it can be seen to the best advantage. With this arbitrary position for the gauge the parts will be considered conveniently as outer and inner, upper or lower, according to their relation in Figure 1.v

On the inner side of the diaphragm support, toward the cover, the support is annularly recessed at 25 to permit collapse into the recess of an annular transversely free flexible diaphragm portion Z6 of a diaphragm 2l. The diaphragm is held at its outer edge by the packing i9 which protects against leakage between the diaphragm support and the cover.

At its center the diaphragm is stiffened and supported to move as a unit, by diaphragm plates or heads 29 and 3Q which are fastened together. The cover is concaved at 3| to give room for the diaphragm and its plates within the cover.

The plates are held to the diaphragm on opposite sides between members 32A and 33, threaded together. One of the members is cupped at 34 for convenient application to it of a desirable form 4 of thrust connection between the diaphragm and parts which are to be moved by it. As in the case of most of the structures, various forms of carrying out my functions are available.

In the thrust transmission shown, the clamp member 32 is apertured at 35 for passage of a pin 35 and the clamp member 33 is coned concavely at Si to form a pin bearing support for the end 38 of the pin 36.

The diaphragm is subjected to differential pressure on opposite sides through pipes 39 and Iii] which may represent differences in fluid level, or in pressure or opposite sides of an orifice, or ow over a Weir, for examples.

The pressure upon the inner face, adjacent the cover, is a standard pressure in the liquid form, shown equal to or greater than the pressure attained due to the highest level of liquid to be indicated.

The pin 36 carries a collar at il in order to prevent accidental withdrawal from the clamping members through aperture 35. At the other end the pin 36 is pointed at 42 to engage within and form a pin bearing with a concavity 43 in a thimble 44 which engages with the spring 45. The end (i6 of the thimble passes through an aperture of the spring and may be peened at 41 to place against the spring to hold the parts together. Peening is not necessary because the parts are under compression.

Whatever the form of connection between the pressure sensitive device (diaphragm) and the magnet, the spring makes a Very convenient support for the horseshoe magnet 48 and supplies eiective retardation for the movement of this magnet.

Where the thimble and pin connection are used, the support of the thimble from the spring and the mounting of the horseshoe magnet may be stiffened and reinforced by holding the horseshoe magnet to the spring by the same bolts 49 which fasten a plate 5i) upon the under side of the magnet, thus uniting the thimble and plate Eil. When this is intended the thimble is flanged at 5l to engage the plate about an opening 52 through which the rear end 53 of the thimble passes. This rear end of the thimble is constructed initially in the shape seen in dotted lines. After it has been passed through the opening it is peened over against the plate in the position shown.

By whatever means the magnet 43 is shifted transversely with respect to its planes and to its lines of ux, whether by a pressure-operated diaphragm or bellows, for example, or as by a float, the means for transmission of the response of the pressure-sensitive element consists basically of passing magnetic flux from a permanent magnet, subject to pressure through a pressure Wall or well 54 to a magnetically susceptible rotatable follower, or armature 55 which is external in the sense that it is free from pressure but at the same time is responsive rotarily to movement of the magnet parallel to the axis of the follower and within the pressure chamber.

More specifically, the magnetic transmission is based on change in reluctance of the magnetic circuit with movement of the magnet at right angles to its flux and along the axis of the armature, accompanied by rotary reaction of the armature to the magnet movement to essentially re-establish the reluctance of the magnetic circuit at a balanced position which is thus maintained as a constant.

It is important that the magnetic reluctance for the balanced position of the armature through the range of movement of the pressure sensitive element remains essentially constant in order to avoid the effect of unbalanced magnetic forces upon the indication.

The magnet is a permanent magnet of material capable of holding its magnetism over prolonged periods of time without change. Its poles 56 and 51 are shown as curved to partly inclose the walls of the well but, where the magnet is canted during its movement along the axis of the armature, the magnet poles must have clearance from the armature sufficient so that the poles will not touch the walls of the well when the magnet has been shifted along the armature axis.

Pole faces have been used successfully which are not curved.

Necessarily with lateral movement of the magnet in the form of Figures 1 to 3 the spring mount in tilting about a lfulcrum will cant the magnet so that its outer and inner surfaces 58 and 59 will no longer be parallel to their positions as seen in Figure 1 and the center line between the poles parallel to their curved surfaces will no longer be parallel with the axis of the armature 55 and of well 54.

In order to give suflicient clearance various means may be used. The total clearance may be made large, or the edges of the poles at 60 and ii! may be relieved to permit this canting with close clearance, or the faces 62 and 63 of the poles may be relatively flattened so as not to present true cylindrical surfaces. The poles may terminate in parallel spaced plane surfaces.

Whatever the means used for insuring clearance, when the magnet tilts as it moves, the poles should be free from contact with the well, throughout the intended range of magnet movement.

While, as suggested, magnets with parallel plane pole surfaces of uniform cross-section may be used with the well located directly between them and with high flux density better results in most cases are obtained with magnet poles shaped to conform as nearly to the well as the law of movement of the magnet will permit and without contact with the well. It is also desirable to keep the clearance as uniform as possible throughout the range of motion of the magnet.

Any good magnetic alloy which is capable of holding its magnetism well can be used for the magnet. Good results have been secured by the use of a cast magnetic material known as alnico. Of course any electromagnet may be used to serve instead of the permanent magnet but practical difficulties of connection, and particularly that it is dependent upon an outside current source, makes this undesirable. With higher iiux densities, smaller magnets may be used.

The magnet movement is desirably as nearly as possible parallel to the axis of the armature and to the axis of the well in order that the clearance of the magnet poles from the well may be made and maintained as small as possible. In such a form as that of Figure 1, with a support which bends about the fulcrum of a spring, the magnet will travel through a curved path determined by the position of the fulcrum and the approach which the bend of the spring about its fulcrum affords to true swinging movement about an axis in the fulcrum.

The armature comprises a spirally twisted strip made of iiat magnetically susceptible ma- 6 terial as close fitting to the well as' possible without contact of the edges of the spiral with the interior walls of thewell, in order that this material may as nearly as possible completely span between the two magnet poles. The magnetically susceptible material is referred to herein variously as magnetizable and magnetic."

The well is threaded at 65 into the housing. It is also threaded internally at 66 and is closed at the outer end by a plug 61. Within the plug 61 and within an insert plug 68' at the bottom of the well are located jeweled bearings 69 and 1B. The plug and the bearing 69 permit passage through theV plug and outer bearing of a shaft 1I rigid with the armature and carrying av pointer or needle 12, counterbalanced by weight 13.

It is necessary, of course, to adjust the indication or recording position to the actual liquid conditions of water level or ow.

Because the gauge depends for its operation upon a higher standard pressure or higher variable pressure with a lower variable pressure, thef standard high pressure where present is used as the Zero point to which the setting of the zero position of the spring in Figures l, 2 and 3 isI related. For this reason the standard pressure or higher variable pressure is introduced to the right of the diaphragm in Figure 1 and the variable lower pressure is introduced to the left of the diaphragm in Figure l.

With a longer pitch the range of movement of a needle 12 is reduced for any given movement of the magnet along the axis of the armature, whereas with a shorter spiral pitch the corresponding range of angular movement and of .iovement of the needle 12 about its scale is increased. Of course the calibration of the scale must be suited to the movement provided.

rihe scale may be calibrated to suit any unusual or irregular needle or pen movement by which it differs from angular movement truly proportional to the change in liquid level or change in rate of flow. In Figure 9 I indicate a correction of the armature movement by variation of the spiral pitch from a true spiral of uniform pitch, and this is intended to apply to any of the forms.

Assuming that the rate of now through a meter or Weir, orice or Pitot tube type, for example, is being indicated or recorded, the need for calibration differently than a uniform calibrated scale may be eliminated or greatly reduced by progressively shortening the pitch of the spiral for the Weir type or progressively lengthening the pitch in the orifice or Pitot tube type with respect to liquid level or pressure variation in the particular meter selected. Where the flow varies with the 5/2 or 3/2 power with respect to the liquid level, according: to the weil' notch used, the pitch of the spiral will be reduced progressively to correspond so as to cause an increasing movement of the needle or recording pen for each successive equal increment of rise in liquid level.

Many examples might be cited where, unless corrected, the needle movement per unit-of pressure difference would vary from uniform movement.

Variation of spiral pitch from uniform pitch to correct the movement of an indicating needle or recording pen responsive to differences in pressure in a flow meter on-oppositesides of an orifice takes care of variation between the two `pressures which may bothY be variable.

In Figure 9 the magnet follower or armature acizeoo 7 55 progressively reduces in pitch 'from the innerv end 'lli to-the outer end lll and the recorder pen 'i5 is correspondingly accelerated in angular movement when the magnetmoves along the follower in this direction with increasing liquid levels or pressure differences.

With orifice flow the armature would be altered in pitch reversely to what is shown in Figure 9, the pitch progressively lengthening from the right to the left as distinguished from the showing in Figure 9, to take care of the square root function applying lto orifice flow.

The zero point of the indicator needle or recording pen can be adjusted by turning the needle or recorder to zero at Zero position of the magnet and setting the needle or pen at its zero by a set screw 'l5 bearing against shaft 1I.

Thev jewel mounting of the spiral armature permits practically frictionless rotation of the armature about its axis, Which is the axis of the well and in practice no dirculty has been found in securing sufhcient angular extent of rotation for direct reading, avoiding the friction and lost motion which would be introduced by insertion of gearing to multiply in needle or pen movement the angular movement of the armature.

The armature is preferably of soft iron or low carbon steel. Excellent results have been secured with Swedish iron and With so-called core iron having high permeability, low reluctance and low hysteresis. An annealed low carbon iron or steel of commercial grade can be used. The armature will operate even when it in itself constitutes a spiral magnet but will not operate as satisfactorily as when it is made of soft iron.

The well is of nonmagnetic material. Silicon bronze has given good results.

The section of the spiral Within the Well which is directly between the poles of the magnet becomes part of the magnetic circuit, the reluctance of which depends upon the angular relation with respect to the poles of that part of the spiral within this range of magnetic influence, i. e. the phase relation of the spiral to the flux at which the delicately mounted armature comes to rest. Since the spiral is free to turn, lowest and essentially constant reluctance considerations cause the spiral to assume a position of lowest reluctance to the magnetic field. Whatever position the magnet poles assume along the axis of the armature, the lowest energy relation of the spiral section between the poles will be the same lowest energy relation and the same phase relation, i. e. the same as that in the initial position of the magnet. Assuming that this always corresponds to alignment of the spiral section at the magnet pole centers with the flux, this will result in such rotation of the armature for any magnet movement that the armature length between the poles will correspond angularly to that seen between the poles in Figure l.

Where the armature pitch is uniform, as in Figure l, the relation of the spiral to the magnet will be constant` i. e. the armature will rotate equally for each increment of magnet movement causing angular rotation of the armature and hence of the indicator or pen to equal extent for equal ranges of movement of the magnet along the armature axis.

The method of transmission of movement of the diaphragm or other pressure-sensitive element into rotative effect upon the indicator results in the transformation of a comparatively small transverse motion of the pressure-sensitive element into a large angular motion of the spiral and yattached pointer or recorder, with an accuracy and reliability quite comparable with that which could be secured if the armature and magnet were coupled mechanically as a Worm and worm gear, but free from gear friction and free from stufng box requirements between the pressure chamber and the indicator.

Basic design considerations indicate that the relation of spiral pitch to magnet thickness should be relatively high. A 4 to l relation gives good results and 3 to l gives quite acceptable performance. The ratio of spiral strip thickness to width is not so lcritical but does affect sensitivity, torque and hysteresis effects. Thin strip spirals show superior sensitivity and lower hysteresis lag while thicker strips show less sensitivity and higher hysteresis lag but with a slight gain in maximum obtainable torque values.

Other forms of adjustment for zero position and for range of indication previously referred to are based upon the mounting and shape of the spring '45, i. e. upon controlling the initial restraint and the variation in restraining force with displacement of the pressure area of the pressure-sensitive element, as applied to the particular type of restraint selected in Figure l. In the present construction this is accomplished by positioning an adjustable fulcrum support (edge) against a at restraining spring such as that of Figure l.

Movement of the fulcrum edge normal to the plane of the spring controls the zero setting, while movement of the fulcrum edge along the surface of the sp-ring parallel to the spring length changes the unsupported spring length and therefore the deflection characteristics. This is equivalent to calibration for range of liquid level travel or range for a given indication.

Space limitations require a special design of the flat spring 'to obtain the adjustment range desired within permissible spring stresses. The spring material mustbe corrosion-proof and free from creep, fatigue and appreciable elastic hysteresis. Good results are obtained with heat treated beryllium copper.

The spring it is sup-ported at its rear end between a transverse block 'll and its cap l, both held to the body of the housing by bolts 79.

lf the supportingv spring were the same thickness and width throughout its length the possible adjustment in range of movement due to fulcrurn adjustment would be relatively small, whereas it is desirable to have the construction cover a range of level difference up to two or more feet. To increase the effect of change in fulcrum the spring can be varied in thickness, or, as is here more convenient and desirable, in the effective width where the spring is bent, i. e., at the fulcrum.

In order to accommodate a wide difference in range, the supporting flat spring is wide and is slotted at d@ at its supported end 8l, the end opposite that which carries the magnet, and the walls adjacent the bifurcation are tapered at 82 and 83. The outer walls taper inwardly and upwardly toward the upper end at 84 and 85.

Though the spring is at all times supported by the block 'il and its cap, the effective length of the spring is determined by an adjustable fulcrurn in the form of a bar 86 having knife edge 8l extending across the spring. The bar 86 is movable transversely to the length of the knife edge, i. e., longitudinally of the spring.

It will be evident that with the taper at the outer end of the bifurcation and the outer edge taper at the upper end of the spring, movement of the knife edge lengthwise of the spring in Figure l will increase the width of the spring which is engaged by the knife edge and consequently will increase the width of spring which must be ilexed in order to bend the spring.

The movement of the knife edge toward the connection with the diaphragm also shortens the leverage available for bending the spring by pressure through the diaphragm, hence, with lowering movement oi' the fulcrum in Figure l, three elements, the progressive (inward) widening of that part of the spring section engaged near the middle of the width of the spring, the progressive (outward) widening of that part of the spring section engaged near the outer edge of the spring and the shortening of the leverage, will progressively reduce the distance to which the spring will be bent by any given pressure exerted through the diaphragm.

The complete range of movement of the magnet and hence of needle indicator or recorder movement for a given water level variation or pressure difference will be reduced progressively by inward movement of the fulcrum knife-edge in Figure 1, or will be increased progressively by movement of the knife edge fulcrum outward in that gure. The fulcrum is shown in Figure l at its outermost position, corresponding with the longest range of movement of the magnet and greatest armature turning movement for a given pressure difference across the diaphragm.

The block carrying the knife edge fulcrum is slotted transversely at 83 from the back 89 so as to permit the block to be slid from the right in Figure l, upon the barrel 95 of a spool 9| having flanges 92 and S3, when the spring is not in place.

The spool is rigid with a screw Sd which is threaded at 95 into the block or at S6 into the flange of the housing, or preferably into both of them, so that a slot 91 in the end of the screw may be accessible for turning to advance or retract the screw, and hence the spool, along the length of the spring. Access to the screw 94 is had through bore S3 within the ange, except as this bore is closed and leakage from within the housing is prevented by a set screw 99 which holds in place packing IBS.

The flanges 92 and 93 hold the bar in position so to place it at any desired position along the length of the spring and to hold it there.

During the travel of the slotted bar lalong the length of the spring, the back of the bar, i. e. the left end face of it in Figure l, engages a disc IBI carried by a screw |82 which is threaded into the housing at 63 and can be advanced or retracted to move the disc lill from or into a recess 164. The control of the screw H52 and the protection against leakage here are similar to lthose shown for the fulcrum screw.

Since the setting of the zero point of the indicator is dependent upon the position of the magnet to right or left in Figure l, the zero point can be adjusted by advancing or retracting the disc l in that figure and correspondingly pushing the fulcrum edge against the spring or releasing it with respect thereto. parts are shown corresponding to that zero position of the magnet farthest to the right in Figure 1.

A limit is set, to the extent of movement of vthe fulcrum edge along the length of the spring toward the lower part of Figure l, by a set screw |65 which is Yengaged by the forward ange of the spool.

In assemblage, the spring-supporting block, range adjusting screw, Zero adjusting screw, limit set screw and fulcrum block are placed in position before the spring with its magnet and other parts is fastened in place by the cap and the cap bolts. The diaphragm and diaphragm support are assembled and put in place, the housing being closed by the cover. The armature, well and associated parts are preferably put in place prior to closure of the cover to check the clearance between the magnet and the well.

The standard pressure and the variant, levelcontrolled pressure, or other opposing pressures are then applied.

By testing with maximum and minimum flow indicating pressures or other opposing pressure, the range of movement of the indicating needle or recording pen is found and the pen or needle is adjusted on the shaft of the spiral to conform to this range. Adjustment is made by advance or retraction of lthe fulcrum bar until the range between high and low level indicating is satisfactory. The zero point -of the needle is then set by the zero-adjusting disc.

With the parts in place and the indicator range and Zero point adjusted, the gauge is operated and any further calibration characteristic of a given installation is effected.

Where a standard pressure is used, the standard pressure is maintained by well known means.' The predominance of the standard pressure on the right of the diaphragm over the variable pressures upon the left of diaphragm tends to bend the spring to the left in Figure l and hence shift the magnet to the left to varying extents depending upon the differential between the variant pressures due to different levels and the standard pressure or due to opposed pressures.

Some of the advantages claimed for the preferred form of'my indicator over other indicators of similar purpose, and to greater or less degree true also of the other forms illustrated by me are as follows:

l. The indicator is mechanical in nature, providing rugged dependable response entirely independent of any supplementary actuating forces provided by such mediums as compressed air or electricity.

2. Although basically mechanical in construction, it is practically frictionless in operation, bearing pivots being restricted to two single point contacts within the pressure space and to two jeweled bearings outside of the pressure space.

3. There are no stufling boxes or other pressure packed movable members projecting through the pressure wall. This eliminates the friction, leakage and other difficulties associated with such types of construction.

4. It is free from gauge glasses, thus eliminating gauge glass troubles and any danger from glass failure or accidental glass breakage.

5. In two of the forms illustrated, it is free from all indicating liquids such as `mercury and other water insoluble liquids. Even in the third form it is free from disadvantages ordinarily associated with such liquids, such as accidental loss of liquid by gauge glass breakageor by blowing out of an indicator tube due to excessive pressure diierentials, discolorationof indicating fluid by dirt particles, bleeding of Vcontrasting colors into adjacent liquid medium, etc.

6. Adjustment to conform to the indication of a conventional type gauge can be eiected while the indicator is connected and in operation.

7. One standardized instrument may, by adjustment, be calibrated to take care of a wide range of indication. This same adjustment may also be used to advantage to compensate for variations in indication due to varying density of liquid with pressure or to special conditions of individual passages. This adjustment may also be made while the indicator is in normal operation.

8. Indication is not limited by standard size of gauge glasses or pressure considerations. rihis permits the use of a clearly Visible pointer moving over a liberally proportioned and well illuminated scale. If desired the scale may be colored and illumination may be external or internal. The effect of contrasting color mediums may also be reproduced if desired and, in absence of pressure restrictions, full and direct visibility at all angles may be obtained.

In Figure 1iL a spring element is used of a different character from that seen in Figures 1-3. In this case a sylphon bellows H is seated in a recess l within the housing cover. The standard pressure is introduced within the sylphon element at 4i), and the preponderance of standard pressure within the sylphon is transmitted through any suitable sylphon head |08 into engagement with a support for a magnet 48 by means of a pin 36.

The magnet support may be itself a spring such as the spring 45, with or without the construction for fulcrum adjustment and for zero adjustment seen in Figure l or any other adjustment.

Permissibly the same train of transmission from the pin may be used, including thimble 44, as in the form of Figures 1, 2 and 3. With this possibility in view, the illustration has been modeled generally upon that of Figure 1.

In order to secure compactness, the sylphon element is shown as entering recess 2| in a ring or disc corresponding generally to the diaphragm support 20 of Figure 1, though this element no longer performs the function of supporting a diaphragm.

The pin carries a collar 4 corresponding generally to the collar 4| in Figure 1. This cooperates with a keeper |09 threaded into the ring 2U'.

With indicator structure in conjunction with a calibrated orice or a V notch flow meter to indicate flow, the resultant flow scale will not be in linear proportion, since the flow is not a straight line function of the pressure difference across the orifice nor of the water level above the Weir. The indication may be made directly proportional to the flow for a given flow condition (or some such approximation to it which will lend itself to ready calibration) by compensating at the pressure-sensitive element of the indicator or at the magnetic transmission.

By the first step above, cooperation could be effected by variable restraint of the magnet movement, as, for example, by introducing a supplemental spring or supplemental springs.

By the second method above probably the simplest way to effect cooperation is by progressive variation of the pitch of the follower or armature to suit the characteristics of a given flow meter as discussed in connection with Figure 9.

In Figure 1b a structure is shown in diagrammatic form also paralleling that of Figure 1, with a spring 45', which may have or may not have provision for adjustment of a fulcrum, and for zero adjustment, but which has one or more supplemental springs ||0 attached to the spring 45' at a selected point or points and attached at their 12 opposite ends at to any fixed structure such as the plate 202.

By the construction in Figure lb the effective component of force from the spring or springs Hi) may be made to increase and greatly alter the total retarding effect of spring 45 as compared with that of spring 45 against movement of the magnet and free end of the spring to the left. The remainder of the construction in Figure 1b showing transmission between a diaphragm and the spring 45 is or may permissibly be the same as in Figure 1.

The operation of the spring or springs iii may supply a considerable part of the retardation effect or may be supplemental merely to a flat spring of any suitable character.

Whatever the type of spring used, a single spring or a composite of two or more springs may be used such as the flat spring and a plurality of spiraled tension springs such as permissibly used in implementing the diagrammatic showing of Figure 1b. The character of spring action may be made to reduce an otherwise wide variation in indicator or recording pen movement for the same difference in pressure, thus bringing these distances within the range of calibration upon a normal scale or record.

In the form of Figures 4 and 5, retardation by springs is wholly eliminated and such retardation as is used is restricted to the progressively increasing pressure of mercury opposing further change and tending to force the parts back to their initial position when increasing pressure upon the surface of a magnet 48 resting in a mercury bath and upon the surface of the bath within which the magnet rests depresses this surface, raising the mercury in another part of the bath subject to a pressure. Here either the standard pressure or the variable pressure can be introduced in the magnet compartment by suitable change in the relation of level to armature, where a standard pressure is used. The illustration contemplates introducing standard pressure at the right.

In Figures 4 and 5, a casing l2 is bored at i3 and ||4 to provide parallel compartments or chambers ||5 and IIG adapted to hold a pool Il' of mercury. The ends of the bores are closed by threaded plugs H8 and H9.

In order that the mercury from one compartment or chamber may communicate with that in the other, the casing between the bores is transversely bored at |20 and the opening through which this transverse boring is effected is closed by a plug |2|.

A Variable pressure is admitted to bore H3 through pipe |22 and inlet |23 and a standard pressure or the higher of two variable pressures to be compared is admitted to bore H4 through pipe |24 and inlet |25.

The magnet 48 floats upon the surface of the mercury in compartment or chamber I5 and in the absence of difference in section or irregularity of weight in parts of the magnet, the magnet will oat level.

Because the magnet is free to move vertically, its upper and lower planes being parallel in all positions to the initial upper and lower planes of the magnet, and because friction of the magnet poles 56', 57 against the sides of a well 54 is not a serious matter when the magnet does not cant during its upward and downward movements, the clearance between the poles of the magnet and the walls of the well may be made less in such a construction than in the other figwaarheen Y13 ures and the edges 60'., 6 I of the pole pieces need not be altered nor trimmed.

With variation of one-and for an orifice ow meter it maybe both--of the pressures to which the mercury bath is exposed in the two compartments or chambers, and with equal cross sectional areas in the two bores, the mercury bath in compartment |I will rise or fall at the same time and to approximately the same extent as that in the other compartment will fall or rise. Difference of the .cross sectional areas of the bores may be used to alter the range of indication for the same Ydifferences in the pressures in the two bores, reduction of the cross-sectional area of compartment l5, in which the magnet lies, with respect to that of compartment IIS increasing the lifting and lowering movement of the magnet and the angular movement of the indicator needle or recorder pen, for example, for the Vsame difference in pressure. It follows of course that if the cross sectional area of mercury in compartment II be made selectively variable along the vertical length of the compartment, the resulting indication will be selectively variable with respect to the difference in pressure between the two compartments and may be made to conform to any variable function of the pressure such 'as flow through an orifice or over a weir.

The reverse is of course also true. 'Ihis pros Vides for adjustment of the scale range. Zero setting may be effected through set screws 7G, or by withdrawal of plug I2I and insertion of mercury or withdrawal of mercury through the opening closed by plug I2I.

The well and armature and their associated parts may be the same well and armature, etc. as seen in Figure 1. Though an indicator needle 'I2 is shown whose indicator target |23 moves over a scale |27, a recording pen and record may, of course, be used as in Figure 10.

In Figure 6 the flow pipe |52, 53 is interrupted to provide flanged terminals |54 and |55 bolted about an orifice plate |56. The flow pipe is tapped on opposite sides of the plate to pipe the pressures from opposite sides of the orifice to a gauge. Both of the pressures in the flow pipe form of Figure 6 fluctuate and the intermediate transmission of the indication or the interpretationfor example calibration-of the indicator must take into account the law of Variation between the two pressures with diierent pressure values and different quantities of flow.

In Figure 6 the pipes |57 an |53 carrying the variant pressures on opposite sides of the orifice plate are connected with any gauge of the character described above, intended to operate by reason of opposed pressures with the higher pressure introduced at the right-hand side of the diaphragm, as in Figure l. The indicator scale |58 is cylindrical.

In Figure 7 the invention is applied to recording fluid flow or indicating merely the rate of :flow of a liquid through a weir meter, a form of Weir being shown at |50 in Weir plate itl in Figure 8.

The water in open feed water heater |52 passes through a valve |53 controlled by any storage space oat, not shown, through a rocker shaft-|54 and rocker arm |55 so as to control the supply of water from the heater entering above the weir and affecting water level |63. Steam pressure in the heater and meter are equalized by pipe |61.

The illustration in Figure 7 is modeled generally after the illustration in Figure 1 in Yarnall Patent No. 1,143,344 .issued June 15, 1915, Yfrom which patent other mechanism normally asso- 114 ciated `with that shown in Figure 7 may be seen and :its operation as well as that of the parts shown in LFigure 7 may be checked and further explained. Other Yarnall patents to Whose structures this invention may be applied are: 1,159,147 to 1,159,150; 1,178,463; 1,200,684; and 1,307,609.

In connection with the types of structure shown in these Yarnall patents, pressure spots IM', |48 are used to carry vapor space pressure as a standard, and variant pressure of the water which is above lthe weir, through pipes |49' and |50 to one of the gauges.

The differences in water level yield corresponding differences in pressure in pipe |50' but do not give :a true indication of the quantity or rate of flow, .since interpretation of water level into rate or quantity of flow involves application of the 5/2 power or other law of the weir, according to the shape of the Weir selected.

lIn Figure 9 a corrective means is shown for producing a uniform or nearly uniform increase in rotation of the follower or armature due to variation in actualflow, where some such relation (law) as the 5/2 or 3/2 power obtains between liquid rate or quantity of flow and height over the weir. By this themovement of the indicator along the yscale can be marked in uniform indicator distancescf movement per unit of flow or can be nearly enough approximated to such uniform flow movement so as to bring any differences within easy calibration limits.

As previously indicated, the armature may be twisted to different pitches, uniform from end to end so that movement of the magnet for the intended distance will yield angular movement to an indicator or pen corresponding with the intended gauge extent of the scale.

Thearmature may also be spiraled irregularly, or according to any progressive rate of change (such vas arithmetical or geometrical ratio, or a quadratic relation for example) to give an approximate straight line indication for rates or quantities of rflow which do not bear a straight line relation to the variant liquid levels or pressures involved.

The spiraled magnetic follower or armature in Figure 9 progressively reduces in pitch from the bottom of the Well outwardly to the spindle or rod 'I I, whereby the same increments of movement of the magnet from the bottom of the well toward the top progressively increase in angular effect upon the armature :according to the law under which the progressive shortening of the pitch has been determined. The follower or armature 55 may thus show v-ariation in pitch according to the law of now inherent in the character of measure used, or the armature may be twisted to compensate ,for deviation which would otherwise take place according to :any irregular determination which maybe found to give the desired correction inindicator record.

Where the departure of the Aneedle from uniform yrotation per unit of ow is slight enough to be within the range of calbration, the well may be of the same character as in the other figures. 'lherquestion o'f whether or not a spiraled armature of suitable Vuniform pitch shall be used, such as seen inFigure 1, or a spiraled armature of progressively Achanging pitch, such as that in Figure '9 becomes a question of policy, in View of the amount of Adeparture of the movement to be indicated from uniform movement per unit of ychange and the adequacy of calibration to take care of this difference.

With ano-rifles flo-wthe law of relation Aof .presl sure difference to ow is the square root law. As a result, the progressive change in pitch of the armature will be the reverse of that shown in Figure 9, though not in the same proportion. The closer pitches will be :at the right.

The movement of the magnet transversely along the length of the armature to secure the desired coupling can be effected Aby hand, whether the well intervene or not.

Figure is intended for the purpose of yshowing that an arm suitable for an indicator, such as 72, can carry a recording pen H8 and travel across a moving record ldisc or moving record strip such 'as the record surf-ace VIS fed from one mounting roll 18e to another at ISI.

The operation in al1 of the forms has much in common, namely, that the movement of the magnetic flux transversely to the lines of flux and lengthwise of the follower or armature disturbs the relation between the follower or armature and the magnet, in the previous position of the magnet in which the Iarmature rests in position of minimum reluctance to the ux, and causes the armature to rotate suiiiciently for the relation of maximum flux to be re-established.

The extent of rotation required to -again establish minimum reluctance `depends, upon the extent of movement of the magnet causing the ux and -upon the pitch of the follower or armature.

It will be evident that the extent of variation in range by adjustment of the lfulcrum is within the control of the designer, who can vary the effect by the extent of tap-er of the spring at different points, for example.

It will be evident that all of the structures illustrated are simple, of low first cost and low cost for repairs. Assembly and external adjustment of the Zero point and range are easy and when adjustment has been made the conditions are stable. The spring afford-s combined spring transmission and entire magnet support an-d makes available more suitable spring material than is otherwise available. It also eliminates difculties associated normally with the use of mercury or other lauxiliary liquids.

The several ways of adjusting for zero [point and for range are not inconsistent but may be used together, one type of adjustment for major adjustment vand other to secure additional adjustment.

It will be evident that the magnetic alignment of an armature with respect yto the flux of the magnet, passing freely through the non-magnetic Walls of the well, aiords a simple, eiective and reliable resilient coupling between the magnet and the armature, at whatever position the magnet may assume along the length of the armature and at the same .time frees the armature wholly from pressure conditions, without regard to the ext-ent o pressure within the chamber traversed by the magnet and whether the magnetic iiux be shifted parallel to `the vaxis of the follower or armature or only generally along the length of the follower or armature.

Since the diierence between the indicator and the recorder ydoes not require more change in structure than the use of a recorder pen upon a travelling record instead of an indicator arrow and since the record to be made is merely a continuous indication, I have aimed to use the word indicator here t-o cover both forms and to apply whether a visual indication only is given or a record is marde.

Whatever the form of structure used by which to turn the spiral armature by movement of fa CTI magnet along the length of the armature axis, I provide a path of magnetic flux across the armature of a width normal to the axis of the spiral and in width :approaching the diameter of the spiral, in order that th-e body of the magnetic flux may not only traverse the metal of the `cross section of the spiral presented at the middle of the poles @but that there Imay be magnetic iux outside of this metal of the spiral on both sides of it and toward t'he respective ends of the spiral, presenting magnetic moments on opposite sides of the magnetic center line, the one tending to turn the spiral in clockwise direction and the other tending to turn the spiral in counterclockwise direction.

Contrary to the -usual cases typical of the structures previously kno-wn, where pole pieces of small dimension with respect to the spiral armature cause alignment of a narrow portion of the included spiral essentially along the straight line path oi the flux between the poles, the present inventio nutilizes poles vof much greater width and breadth, so las to include the width of the armature and an axial length of the armature approximately equivalent to one-fourth of the spiral pitch within the magnetic field, and preferably in the range between one-eighth and one-quarter pitch, but permissibly in the range vbetween oneeighth and three-eighths pitch.

The length of spiral influenced by the magnet ilux may be greater or less than one-quarter pitch length of spiral but optimum performance will not then be realized.

The larger area and the location of the pole permit not only alignment of the center portion of the armature with the flux as in other devices but also include a spiral section on each side of the center line which is subjected to opposite magnetic torques since the spiral sections at the faces of the magnet will be at an angle of about 45 with the flux line if the one-fourth pitch relation is used.

Practical operation of the indicator requires a strong, compact, independent source of magnetic flux to bridge the gap occasioned by the pressure wall and by the necessary clearances between the magnetic poles and the spiral armature. This calls for a permanent magnet of eflicient magnetic material and a magnetic circuit of minimum reluctance. A horseshoe type magnet satisfies the latter requirement.

Oppositely disposed bar magnets would not provide a magnetic return path of low reluctance for the flux and the iux density across the gap for the same magnetic weight would only be a fraction of that provided by the horseshoe type. Such a structure utilizing the best known magnetic materials would be too inefficient for prac tical operation of the indicator.

If a low reluctance path be provided for two oppositely disposed bar magnets, the resulting structure would in eiTect constitute a composite horseshoe type magnet.

Electromagnets, although theoretically applica ble, are ruled out because of objection to dependence on an outside source of energy. The practical diiculty of conveying current to and from a movable magnetic coil immersed in a conduct ing liquid and contained in a pressure vessel makes this form additionally objectionable.

Sensitivity considerations require that the ux emanating from the poles remain as iixed as possible with respect to the poles so as to cause total armature response and minimum tendency for shifting of the ux concentration on the 17 pole pieces or faces to accommodate slight positional changes. The magnetically soft cores customarily used with electromagnets do not appear to satisfy optimum requirements in this respect.

The complete magnetic circuit is shown in a horseshoe type of permanent magnet which may be referred to as an open ring type permanent magnet or as a permanent magnet having opposite holes directed toward each other. The open ring shown is a ring in which the circuit has been interrupted by removing a portion of the material which would otherwise be required to complete the ring, which has been magnetized and in which under the conditions given the ends of the otherwise complete ring structure present themselves as oppositely facing poles.

The magnetic screw is in itself old. It is shown, for example, in Norwegian Patent No. 46,537; German Patent No. 515,342 and in U. S. Patent No. 2,154,678.

The distinctions and the reasons for the distinctions of the present invention from such structures will be clear from the following discussion.

Armature response in the patents above in general results from the continuous alignment of a narrow cross sectional band of spiral armature with longitudinal movement of a transversely directed field of magnetic flux. Maximum sensitivity of operation for this condition requires minimum clearance between magnetic armature and poles or pole pieces conforming to the adjacent section of the spiral precisely as indicated in the illustrations. If the gap between the armature and magnetic poles be increased, the reluctance of the magnetic circuit is increased, the flux is decreased, and a loss of torque and sensitivity results. Interposition of a pressure wall and necessary clearances between poles and armature as applied to the present case would necessarily increase the gap and consequently would result in the lowering of the level of performance of the structures of these patents.

In the present case a comparatively long section of the spiral armature (approximately onefourth pitch) is contained within the gap between broad poles of a strong Alnico magnet (the most efiicient commercial permanent magnet material available to date). The flux is not guided or directed to the opposite edges of the included armature as in the patents, but streams across the gap and acts upon the entire included spiral of approximately one-fourth pitch length. The spiral section at the magnetic centerline of the poles is aligned directly across the poles and in this respect behaves similarly to the patent structures. A 45 twist of the spiral on each side of the center line is also in the magnetic field and the spiral armature is thereby subjected to equal and opposite turning moments. The relation of magnetic pole width to spiral pitch is selected by me so as to provide maximum or near maximum opposed turning moments in the planes corresponding to the sides of the magnet along the axis of the spiral armature, for this condition causes maximum unbalance for an increment of movement and provides the amplitude of restoring torque and sensitivity necessary to fulfill requirements of the present case.

In Figures 11-11a, 12--12a, 113-13a and 14-143, a previously existing form of magnet poles operating upon a twisted spiral between them is shown. As is usual in such cases, the magnet poles are both short in extent along the axis and thin, i. e. they not only do not extend far along the armature axis but they do not extend far about the armature. The pole areas are thus not only circumferentially small and small in their axial extent but are small in their total areas. They concentrate the ux upon that intermediate portion of the spiral armature which is immediately adjacent at the middle of the poles. As a result they give substantially a straight line iiux path from one pole to the other through the included Isection of the armature.

For comparative purposes, unit effective magnetic pole area is assumed and the magnetic force is assumed `to .be unity at minimum gap distance. In the equilibrium position of the armature, the moment arm of the magnetic force is zero, the spiral section being in alignment with the flux. The torque is of course also zero.

In Figures l1 and 11 it will be seen that the poles |82, |83 have a total width substantially equal to the thickness of the strip |84 from which the armature is spiraled. The gap indicated has been made excessive so as to accommodate an intervening pressure well, as would have to be the case if this form is to be compared with that of the present invention. The length of the pole pieces parallel to the armature axis from points |85 to point |86 is trivial as compared with the pitch of the spiraled armature. The volume of the ux or the cross section of the iiux, as it may be considered, is very small as compared with the section of the spiraled armature through which the flux distributes.

The structure of Figures 11 and l1a is best suited to conditions where the poles can be brought close up to the intervening spiraled armature and where the entire iiux can be concentrated for this reason upon a short section of armature. As will later be pointed out, it is not well suited to a construction where the armature is surrounded by a protective well which makes it necessary to space poles from the spiraled armature to such an extent that the magnetic flux cannot be concentrated upon the armature. In such a case as that in Figures 15 and 15a, the structure of Figures 11 and li.a would be inadequate for the purpose.

In Figure 12 the magnetic force for equilibrium corresponding to Figures 11 and 11L is shown. The magnetic force is given per unit effective pole area. The magnetic force exerted is represented by the figure |81 in the maximum position when the armature is aligned with the iiux. The curve in Figure 12a indicates the effective force exerted by the pole pieces upon the armature with movement of the poles along the axis of the armature a distance equal to one-fourth oi the spiral pitch.

In Figures 13 and 13EL the moment arm of the flux acting upon the spiral armature is indicated as reaching a maximum when equal to r the radius of the spiral, shown at |88. The moment arm of the ux tending to turn the spiraled armature about its axis is zero when the transverse section of the armature is in alignment with the iiux. As the magnet is moved along the spiraled armature the moment arm increases, reaching a maximum at some such point as |39 at a distance corresponding to somewhatover one-eighth of the spiral pitch distance. The torque exerted upon the spiral armature tending to turn it about its axis under the conditions in the gures above is represented in Figures v14 and 14e This is a product of the magnetic forces and the moment arm. The position longitudinal magnet movement is a function of the restoring torque with relative displacement from the equilibrium position. In the case of Figure 12, the magnetic force increases from assumed unity per unit of area with relative displacement of magnet and armature and the moment arm decreases from zero with this progressive displacement, as shown in Figure 13. The resulting form of the torque curve with respect to change of relative position of magnet and armature is as shown on Figure 14. It will be noted that the maximum restoring moment is developed for a magnet movement of slightly over one-thirty-second of the spiral pitch distance.

In Figures to 19, 15a and 16a inclusive, the schematic views shown apply to the present form of the invention as distinguished from the prior art type discussed in connection with Figures 11, 11a; 12, 12a; 13, 13a and 14, 14a.

In the present invention the thickness of the pole pieces from |92 to |93 preferably is several times the thickness from |94 to |95 of the strip material from which the spiral armature of magnetizable material is constructed (as this exists in the prior art of Figure 11, for example), and my best results have been obtained when the chord distance approaches the diameter of the armature. This gives a much wider band of flux across throughout the depth or height of the magnet pole pieces |82 and |83'.

The extent of the pole pieces from |85 to |86 parallel to the axis of the armature is also many times the extent in the prior art form from |85 to |86 (see Figure 11a) and my best results have been attained when the pole pieces approximate one-fourth of the pitch of the spiral armature |86.

Between the spiral armature and the pole pieces there is space at |96 for the stationary pressure shield, within which space the armature rotates and outside of which the pole pieces move parallel to the .axis of the armature. These general relations are shown in Figures 15 and 15a.

The illustrations in Figures 15, 15a; 16, 16a; 17; 18 and 19, which schematically show the present invention, form a basis for contrast with the prior art form of the immediately preceding schematic gures. Of these gures, Figures 15 and 15e show the contrast between the wider pole pieces, extending farther along the armature axis, of the present invention and the pole pieces of small dimension in both directions and of small cross section in Figures 11 and 11a.

Figures 15, 15a yield a wide range of variant magnetic forces .and movements effective on the spiral section included in the magnetic field of large cross section provided by the present invention.

Assuming, as before, that unit effective magnetic force per unit area obtains for minimum gap distance, we nd this unit force acting on the edge of the spiral to be maximum at the mag--A netic centerline and reducing toward the magnet sides because of increasing gap and decreasing projected armature areas between the spiral edge and the centerline, the spira1 edges acting farther and farther away from the pole faces as the distance along the axis increases on opposite sides of the centerline.

Figures 16 and 16a show the relative magnitude of these magnetic forces and the approximate totals `at the various spiral sections within the magnetic gap. The moment arm of these respective total forces is zero at |91 at the centerline of the magnet (Figure 17) and increases in opposite directions on each side of the centerline as there shown. K

The moment arm reaches a maximum at the limits |98 land |99 at each side of the magnet as shown in Figure 17. The resulting torque, which is the product of the total forces and corresponding moment arms at the respective sections, increases in opposite directions at each side of the magnetic centerline and reaches a maximum at the pole limits as indicated at 29E) and 20| in Figure 18. The spiral assumes a balanced position of equalization of opposed moments which corresponds to the position of lowest reluctance of the magnetic circuit.

In the entire operation described, it makes no difference which be the leading and Which the trailing edge of the pole pieces nor, correspondingly, does it matter whether the magnet is moving upwardly or downwardly, the character of' operation of the armature by the magnetic forces set up being the same.

In the case of Figures 15 and 15a, axial magnetic movement of the magnetic poles with respect to the spiral armature adds to the existing torque on one side of the magnetic centerline and subtracts from the existing torque on the other side, at or near the maximum obtainable ra e.

Although the torque per unit magnetic force per unit area may be comparable for the prior art discussed in connection with Figures 11 to 14 or even less in the present invention, the larger effective pole and armature areas of the present invention provide for much larger total magnetic restoring moments. It will be noted that the initial rate of increase in the restoring torque with relative displacement of the armature and the magnet is high and likewise contributes to sensitivity of response.

The curves of Figure 18 illustrate the development of this greater restoring torque. The left hand curve 292 shows the relative torque values developed in the spiral armature within the magnetic gap. It will be noted that the torque is zero at the magnetic centerline 203 and increases equally in opposite directions to a maximum at 200 and 29|. It will thus be evident a distinct advantage exists in having the axial extent of the magnet pole piece the greater part of a quarter of the pitch distance.

The restoring torque comparable to that in Figures 11 to 14 may be obtained by totalling the unbalancing moments per unit edge area of spiral with respect to magnetic movement. This can be done graphically by dividing the spiral length in the magnetic gap into increments 204 of length corresponding to the assumed unit length of the magnet represented in Figures 11 and 11a and adding the mean torque values of these increments as they become unbalanced moments with respect to magnet movement.

To illustrate the above, take the case of mag- 'net movement corresponding to one`unit I of length in Figure 18 which, for the relations shown, corresponds to one-thirty-second of the distance of the spiral pitch. A positive torque loss of t1 results from this movement, accompanied by a simultaneous gain in negative torque t2 of approximately the same magnitude. The net relative restoring torque for this magnet movement would be ti-l-tz. This point is plotted on the torque vs. magnet-movement curve for the movement of one-thirty-second of the spiral pitch distance (as shown by Figure 19). Further magnet movement develops additional restoring torque as indicated by the completed curve of the same figure.

It will be noted that the maximum restoring moment occurs at a magnet movement equal to one eighth of the spiral pitch from the equilibrium position. rlhis is advantageous in that it provides latitude of positive armature control and response for rapidly changing magnet positions as compared with the comparable cases in Figure 14.

The utilization of the magnet poles of relatively large size with respect to spiral armature dimensions of the present case contributes important advantages aside from the foregoing distinctions. It permits retention of higher unit magnetic forces and provides greater assurance of permanency of magnetic properties over the life of the instrument. These advantages furthei` amplify the improved performance over that of the patent structures and in themselves provide the practical elements which stimulate commercial acceptance of a device. The form of the magnet used furthermore conforms to simple design and emcient proportioning of magnet material. This in turn implies low cost of manufacture commensurate with high level of performa-nce.

A more detailed mathematical analysis of forces and moments can be prepared if it be desirable to distinguish the present invention from the structures shown and described in the Norwegian and German patents and in the patent to Hawthorne and Campbell previously referred to. However, the eiectiveness of such an analysis must depend upon recognition of the basic differences indicated herein.

It would seem to be clear that the differences between the operation of the structure of these prior patents and the operation of the present invention is a radical difference necessary for operation where there is to be a large gap to provide for a pressure protective well and is a diierence in kind and not a mere difference in degree. The structures of the type shown in the Norwegian and German patents or in Hawthorne above would be inoperative for my purpose and could not be made operative without the radical change in character of the flux eld represented by the present invention.

One noticeable difference between the structure and method of Figure ll and that of Figure l5 lies in the means by which balance is secured.

In Figure 11, the armature is held in position of equilibrium by the magnetic force represented by a pull of force a directing the armature section shown toward pole 182 and the magnetic force b directing the armature toward the pole i233. The pull of force, a and b whose lever arm is zero in position of equilibrium increases with rotating movement of the armature to become a and b when the armature is rotated to the position shown in dot and dash.

On the other hand, remembering that in Figure 20 the section (pitch quadrant) ci the spiral length at any time lying between the poles has strip edge ends 235 and 206 toward the observer at one end of the pitch quadrant being considered, and at from these facing ends has edge ends 261 and 208 away from the observer, there are two pairs of forces both acting on lever arms at the same time, namely c and d, both acting upon the edge ends of the armature facing the observer and both tending to rotate the armature in counter-clockwise direction by the pull exerted on these ends by the portions 269 and 2,16 of the magnet poles. This forms one pair or couple of magnetic forces.

t the opposite edge ends 267, 2GB of the quadrant section of the armature are locatedV two magnet moments e and f operating between the edge ends 201 and 2% and the portions 2| I, 212 of the magnet, both tending to pull the more nearly adjacent edge ends toward the corresponding part of the magnet, forming a second pair or couple which tends to rotate the armature in a clockwise direction.

Both of these pairs of magnet moments operate on lever arms, which are not zero in theposition of equilibrium in Figure 20-thus contrasting with Figure 11. In this position of equilibrium the lever arms approach one-half of the diameter of the spiral.

There are, therefore, two pairs of balanced magnetic moments in Figure 20, both of which operate with maximal lever arms and with their torques opposing each other. Each movement of the magnet from equilibrium increases the torque of one pair and reduces the torque of the other pair, the addition and reduction taking place at the points of greatest leverage. Let us consider for the moment that the movement reduces the force acting upon the nearer end, i. e., reduces the forces c and d tending to rotate in counter-clockwise direction and increases forces e and f tending to rotate in clockwise direction. The clockwise forces will overcome the counterclockwise forces and the armature will turn until they equalize.

It should not be inferred from the distinctions drawn that the patent structures are not properly operative in their own elds. If the magnetic gap of Figures 11 and 11a is reduced to about one-tenth of that shown, which brings the structure in approximate relation to the proportions of the patent structures, the flux is increased ten times and the magnetic moment arm for a given displacement is increased in approximately the same order. This will without question result in good operation, even with far less eiiicient magnet materials than are applied in the present case. This same case which illustrates the rate of increase of torque with reduction in the gap demonstrates the unavoidably high loss of torque with increase in the gap to accommodate the pressure wall of the present case. This in turn emphasizes that the patent structures were intended for applications involving close clearances between armatures and magnet poles and are inadequate if attempt be made to apply them to the present case.

In summary, the following distinctions may be drawn: the patent structures operate by positioning of the armature to a balance at essentially zero value of opposed magnetic moments. The present case operates by positioning of the armature to a balance at maximum equal and opposed magnetic moments. In other words, the

23 patent structures operate by the setting up of restoring torque forces starting from zero and the present case operates by restoring torque caused by unbalancing o opposed magnetic moments (at or near the maximum obtainable rate) with respect to change in positional relationship of the magnet and the armature.

Stated in still other terms, the patent structures are operated by the development of a pair of magnetic moments with relative displacement of the magnet and the armature from the balanced position, While the present case is operated by the additive unbalance of two respective pairs of opposed magnetic moments with displacement of the magnet and the armature from a balanced position.

The patent structures utilize poles or pole pieces of restricted area to effect conformation of the flux path to the effective armature section o spiral. The present case utilizes large poles, which secure excellent results when they approach the diameter of the spiral in one direction and when they extend over approximately one-quarter of the spiral pitch distance in the other, producing a correspondingly strong magnetic field, effective over a comparatively large area and providing a large margin of magnetic response necessary to meet the practical requirements of the case.

Again the patent structures operate by diametral alignment of a spiral section with the flux, while the present case operates by axial equalization of moments acting on the projected spiral areaJ within the magnetic gap.

The present case provides for much greater restoring torque over a wider range of magnet movement than that provided by the otherwise corresponding structure ofthe patents. The larger magnet provides for higher overall magnetic strength per unit pole area, and a higher degree of permanency of magnetic properties and lends itself to simple, economical and practical design.

In view of my invention and disclosure variations and modications to meet individual whim or particular need will doubtless become evident to others skilled in the art, to obtain all or part of the benets of my invention without copying the structure shown, and I, therefore, claim all such insofar as they fall within the reasonable spirit and scope of my claims.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. In a ilow meter having a space in which liquid flow occurs provided with walls including an orifice in the path of the flow, having a movable Wall and having conduit connections from points on either side of the orifice to points on either side of the movable wall for causing movement of the wall in response to pressure, magnetic flux producing means moved along a range of longitudinal movement by the movable wall in response to the diierential pressure from the opposite sides of the orifice, a spiraled armature of magnetic material having a variable pitch positioned in the flux path and extending along the path of movement of the magnetic ux producing means, the variation in pitch of the spiral correcting the non-linear character of the relationship between flow and motion of the 24 ux producing means, bearing means pivotall'y supporting the armature to rotate about its longitudinal axis and an indicator mounted on the armature for indicating the angular position of the armature.

2. In a flow meter having a space in Which liquid flow occurs provided with walls including an orice in the path of the flow, having a movable wall and having conduit connections from points on either side of the orifice to points on either side of the movable wall for causing movement of the wall in response to pressure, magnetic flux producing means moved along a range of longitudinal movement by the movable Wall in response to the dii-Ierential pressure from the opposite sides of the orifice, a spiraled armature of magnetic material having a variable pitch positioned in the flux path and extending along the path oi movement of the magnetic iiux producing means, the variation in pitch of the spiral correcting the nonlinear character of the relationship between flow and motion of the ux producing means, bearing means pivotally supporting the armature to rotate about its longitudinally axis, a pressure wall surrounding the armature and betwen the armature and the iiux producing means, and an indicator mounted on the armature.

3. In a iiow meter having a pressure responsive member which responds to pressure developed lby reason of ilow, a horseshoe magnet connected to the pressure responsive member and moved by reason of the pressure applied to the member and in a nonlinear relation to the ow, a magnet support retarding movement of the magnet, walls forming a chamber within which the horseshoe magnet moves and including a nonmagnetic armature well extending between the poles of the magnet, and extending along the path of movement of the magnet, a magnetizable spiral armature mounted ior rotation about its longitudinal axis within the well, the spiral differing from uniform pitch in accordance with a nonuniform relationship between pressure and flow to promote uniform rotation proportional to the rate of flow, and means for indicating the angular extent of rotation of the armature.

WALTER J. KINDERMAN.

REFERENCES CITED The following references are of record in the le of this patent:

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